wiring question

If the ammeter is not in good shape, I'd either bolt them back together, or pull the ammeter apart and see if you can repair it. One thing that is NEEDED on many of those ammeters is to solder the studs to the "guts" AKA the shunt inside.

This is a great article on some of the troubles

http://www.madelectrical.com/electricaltech/amp-gauges.shtml
There is also a way, depending, to convert that spot to a voltmeter

https://www.forabodiesonly.com/mopar/threads/ammeter-to-voltmeter-who-does-it.119480/
This thread:
https://www.forbbodiesonly.com/moparforum/threads/dissection-and-study-of-a-mopar-ammeter.199179/
Soldering the ammeter studs if they are loose
https://www.forbbodiesonly.com/moparforum/attachments/img_1084-jpg.982964/

The gist of the entire ammeter problem:

1...Ammeter circuit wiring,really, is too small, especially if you go big on an alternator
2...Bulkhead connector terminals are not adequate, same deal
3....Ammeter studs are only making tight contact because of the "sandwich of being installed with the studs, shunt, insulator washers, nuts, etc. If any of that gets loose, it gets hot, and then gets more loose......